Hi,
I am affraid I do not understand Your advice. Synology NAS and docker container are running with CET zone.
Synology NAS:
root@NAS01:~# date
Mon Jan 18 09:22:16 CET 2021
checkmk docker terminal:
root@checkmk-check-mk-raw2:/# date
Mon Jan 18 09:27:44 CET 2021
Timezone set with container variables:
What shall I change more ?
Below notification example: